1. Field of the Invention
The present invention relates to a silver halide photographic material adapted for processing with a lith developer using a hydroquinone compound as the sole developing agent, or an ordinary hard-tone black-and-white developer using both a hydroquinone developing agent and a superadditive developing agent. More particularly, the present invention relates to a high-speed silver halide photographic material having good storage stability and an adequately high tone.
2. Description of the Prior Art
A technique is known in which the interior of a silver halide grain is doped with a rhodium atom in order to provide the former with a hard tone. This method is extensively used because a silver halide photographic material having a desired tone can be obtained by controlling the content of rhodium with which the interior of each silver halide grain is to be doped.
A silver halide photographic material having a rhodium salt doped in the interior of a silver halide grain can be provided with a hard tone, but it often experiences a deterioration in other photographic characteristics, such as reduced sensitivity or becoming soft during storage. In order to eliminate these defects, U.S. Pat. No. 3,488,709 and other prior art references propose the addition of a cadmium salt concurrently with the manufacture of silver halide grains containing a rhodium salt. However, this method is not practically feasible because excess cadmium salt may cause environmental pollution or toxicity to humans not only by being discharged in effluent from the manufacturing line but also by being carried over into the used developer, fixing solution or washings during the processing of a finished photographic material.
In order to solve this problem, Japanese Patent application No. (OPI) 11029/1977 (the symbol OPI as used herein means an unexamined published Japanese patent application) and other prior art references propose stabilizing the cadmium salt by incorporating a compound such as hydroquinone. However, even this method is not capable of permitting the rhodium atom to exhibit its hard tone imparting effect without sacrificing the sensitivity and storage stability, and hence requires a further improvement.